Ever wonder what would have happened if Ernest Hemingway had asked Salvador Dali to illustrate "The Old Man and the Sea"? Probably not, but the idea itself is tantalizing -- a book filled not only with powerful words but also masterful illustrations, playing off of each other to tell a story in both figurative and literal symbols.

Although it's far too late for a Dali-Hemingway collaboration, there's still hope for other significant works blending illustration and text in the form of graphic novels.

Pinning down an exact definition is difficult because there's no consensus on what constitutes a graphic novel, but there are some noted differences. For starters, graphic novels are typically much longer than the average comic book. Secondly, most comic books are part of a series, issued monthly, while graphic novels are often one story per book, sometimes spread over multiple volumes. Graphic novels are also typically square-bound like books.

Beyond these disparities, though, comics and graphic novels are strikingly similar. They both have illustrations, rely heavily on fonts to drive the stories, and are usually laid out in boxy frames that resemble comic strips. Like their comic kin, graphic novels are a type of sequential art. They're a type of novel with a narrative that's conveyed through both text and drawn art. Each page's layout includes panels, or boxes, with borders that separate them from other panels on the page. Usually, these panels are square or rectangular, but this is not always the case; the genre's free-form, experimental nature makes it harder to classify precisely. Between each panel is the gutter, which is simply blank space.

Like white space in any sort of visual art, carefully constructed gutters add to the flow of the novel. A wide gutter around one panel, for example, might give that particular frame a greater sense of importance. And like all comics, graphic novels use thought or speech balloons (also called bubbles) to show what a character is thinking or saying. In essence, they're quite a bit like comic strips.

These novels, though, are anything but the Sunday funnies. They usually have longer and much more complicated storylines and themes. The artwork is intricate and the carefully constructed page layouts become part of the work's message. These criteria for defining graphic novels might seem simple enough, but there are a lot of misconceptions about this art form. For clarity's sake, it helps to explain what graphic novels are not.

Graphic novels are not books with pictures thrown in for good measure. They're not movie scripts, although with the recent spate of graphic-novel-based Hollywood flicks, you might think otherwise. They also are not simply a collection of many comic books bound together (those are called trade books or trade publications), although it's now common for serialized comics to be published later in graphic novel collections. And some people argue that graphic novels aren't really even a genre of comic books; they're an independent artistic medium that's different in the way that music, poetry and sculpture are all unique.

One thing that's not debatable, however, is the fact that graphic novels are getting more and more popular. In 2006 alone, sales for graphic novels hit around $330 million [source: Beneath the Cover]. In dollar amount, that's more than four times as much as in 2001. Next, you'll see how graphic novels are adding evermore zam, blam and pow to their pages -- especially compared to their ancestors.